Fuel sending unit wiring

paddyrk

Member
Jun 7, 2018
71
4
18
Dublin, OH
I have a 1991 lx v8, and am trying to wire a custom fuel gauge. It is with the Holley hp efi system, but it’s not getting a reading. I have the yellow/white wire from the dash connector wiring into it and it is setup as a custom ohms input, but does not display a read out, meaning ♾ ohms, because it reads as 100% full no matter the scaling or boundaries. I have tried looking at wiring diagrams for the sender but I can’t figure it out. I assume the sender is grounded on its own away from the dash cluster connector, but I could be wrong. If anyone could help, it would be much appreciated.
 
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paddyrk

Member
Jun 7, 2018
71
4
18
Dublin, OH
Ok do some testing before dropping the tank.
I didn’t an ohm test, positive test on the yellow/white fuel sender wire, negative on the negative battery terminal, and it read about 56 ohms. Would me completely removing the factory gauge cluster and only jumping the green/red wire to a switched +12v source mess with the grounding of the sending unit?
 

paddyrk

Member
Jun 7, 2018
71
4
18
Dublin, OH
ok... the canbus is usually reserved for communication with the ECU. let me look at the wiring diagram again.
Okay, not sure if you saw me edit my earlier post, the only cables I messed with from the factory dash connectors were the red/green that I attatched to a switched source, and the yellow/white fuel sending unit wire, I’m wondering if me not changing any ground messed it up
 

paddyrk

Member
Jun 7, 2018
71
4
18
Dublin, OH
not sure without knowing how the holley is wired. trying to help on my phone is a pain. lol
And I appreciate it greatly, you may have seen this already but I went and grabbed the wiring diagram for the system I am using
 

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